1. Field of the Invention
The field of the invention relates generally to eyewear and more specifically to eyewear lenses, such lenses having optical properties enhanced for night driving.
2. Description of Related Art
Eyewear is commonly used to correct vision errors, aberrations and focusing deficiencies caused by age, disease or other factors. In addition to correcting physiological vision problems, eyewear may also be used to ameliorate physical or environmental conditions (such as glare, variable lighting, high intensity light, dust, condensation, etc.) that can affect sight.
One challenging condition for human vision is night driving. Several common occurrences in night driving are known to interfere with good vision, including momentary blindness from oncoming headlamps, glare and discomfort from following drivers' headlamps and reflections in rearview mirrors, tail lamps, and weather effects causing light scatter and decreased visibility. In addition, age-related changes in the eye can reduce visual ability while driving at night, as discussed, for example, in the article “Why HID headlamps bother older drivers,” M. A. Mainster and G. T. Timberlake, British J. Ophthalmology, 87: 113-117 (2003).
The eye has a light sensitivity range of over twelve orders of magnitude. Typical bright daylight luminance (in cd/m2) ranges from over 1,000,000 to about 1000 cd/m2, dusk is approximately 30-0.1 cd/m2, bright moonlight is approximately 0.01 cd/m2, and an overcast night with no moon is about 0.0001 cd/m2. Different structures within the eye, the rods and cones, allow extended response and accommodation over such a wide range of conditions. However, under lower ambient light conditions, the eye's recovery time is much slower after sudden exposure to a bright light source; the eye's receptors are saturated, and commonly need ˜10-60 minutes to re-adapt. Thus, exposure to bright headlamp light (which can easily range from 30-5000 lumens) when the eye has accommodated to lower light levels will saturate the eye's response, and compromise vision. Attenuation of light is a good method to reduce glare and momentary blinding effects from sudden exposure to bright lights. However, the low level of ambient light in night driving conditions means that any reduction in illumination is potentially deleterious to the safety and ability of the driver. Thus, it is not obvious that attenuation or filtering of light can be a successful approach to improve night driving vision.
Lens filters have been employed or proposed in the prior art for enhancement of vision in bright daylight conditions, but in these instances excess light is being removed to allow the eye to more efficiently respond to the high ambient illumination levels. For example, U.S. Pat. Nos. 5,235,358, 5,975,695, 7,106,509 B2, 7,278,737 B2, and U.S. patent application Ser. No. 13/029,997 (published as 2011/025505) all describe filters that substantially or completely block transmittance of light in one or more visible wavelength regions. In addition, light that is potentially damaging to the eye, such as ultraviolet or high-energy blue light, may be preferentially blocked. Given the very limited light available for night driving conditions, however, blocking substantial amounts of such night-time illumination would not seem advisable.
There have been previous methods to modify lenses for eyewear (such as spectacles or goggles) to aid with the visual problems of night driving. Some of these have employed lenses wherein one portion of the lens is clear, and another portion is tinted, translucent, polarized, reflective or otherwise changes the light exposure to the eye. Various shapes, distributions and locations of the clear and light-attenuating regions on the lenses have been presented. U.S. Pat. No. 8,192,021 B2 describes another arrangement, in which the central portion of the lens is yellow-tinted to absorb blue light, while the periphery is red or orange to absorb light below 600 nm. Given the wide variety of techniques and products described, it is clear that a universal answer to concerns with night driving has not been achieved.
The present invention offers a new approach to address the concerns with exposure to bright light when night driving.